In many types of rotating rigid disk files, each of the read/write transducers (or heads) is supported on a carrier (or slider) which rides on a cushion or bearing of air above the surface of its associated disk when the disk is rotating at its operating speed. The slider is connected to a linear or rotary actuator by means of a relatively fragile suspension. There may be a stack of disks in the disk file with the actuator supporting a number of sliders. The actuator moves the sliders radially so that each head may access the recording area of its associated disk surface.
In these conventional disk files the slider is biased towards the disk surface by a small force from the suspension. The slider is thus in contact with the disk surface from the time the disk file is turned on until the disk reaches a speed sufficient to cause the slider to ride on the air-bearing. The slider is again in contact with the disk surface when the disk file is turned off and the rotational speed of the disk falls below that necessary to create the air-bearing. In such contact start/stop (CSS) disk files a lubricant is often maintained on the disk surface to prevent damage to the head and the disk during starting and stopping of the disk.
One type of disk for use in rigid disk files is a thin film metal alloy disk which typically comprises a substrate, such as an aluminum-magnesium (AlMg) alloy with a nickel-phosphorous (NiP) surface coating, a cobalt-based alloy sputter deposited as the magnetic layer on the substrate, and a protective overcoat, such as a sputter-deposited amorphous carbon film, formed on the magnetic layer. U.S. Pat. No. 4,503,125 describes a protective overcoat of amorphous carbon formed by sputtering a graphite target. Assignee's U.S. Pat. No. 4,778,582 describes a protective hydrogenated carbon overcoat formed by sputtering a graphite target in the presence of Ar and hydrogen (H.sub.2). In addition to the magnetic layer and the protective overcoat, thin film disks may also include a sputter-deposited underlayer, such as a layer of chromium (Cr) or chromium-vanadium (CrV), between the substrate and the magnetic layer.
In addition to the above-described conventional CSS magnetic recording disk files, disk files have been proposed wherein the head-disk interface includes a liquid film as a liquid bearing between the transducer carrier and the disk. An example of this type of liquid-bearing interface disk file is described in assignee's pending application, U.S. Ser. No. 264,604, filed Oct. 31, 1988, and published May 9, 1990 as European published application EP 367510.
A problem in both conventional air-bearing interface disk files and the proposed liquid-bearing interface disk files, both of which may use thin film disks as described above, is the suitability of the disk protective overcoat to provide resistance to wear caused by contact of the carrier which supports the magnetic recording transducer.
In order to improve the wear resistance of the disk it is necessary to make the disk surface as smooth as possible. However, a very smooth disk surface creates an additional problem known as "stiction". In the case of air-bearing interface disk files this means that after the slider has been in stationary contact with the disk surface for just a short period of time, the slider tends to resist translational movement or "stick" to the disk surface. This "stiction" is caused by a variety of factors, including static friction and adhesion forces between the disk and slider created by the lubricant. Stiction occurs even with smooth unlubricated disk surfaces because of the strong intermolecular attraction at the interface between the smooth disk and slider surfaces. Stiction in a disk file can result in damage to the head or disk when the slider suddenly breaks free from the disk surface when disk rotation is initiated. In addition, because the suspension between the actuator and the slider is relatively fragile in order to permit the slider to fly above the disk surface, sudden rotation of the disk can also damage the suspension.
In order to minimize stiction, the disk substrate may be mechanically textured so that the overlying protective overcoat, which will generally conform to the surface topography of the substrate, presents a "textured" surface to the slider. However, while a textured disk surface may be conducive to stiction reduction, as previously explained a textured disk surface may have inferior wear resistance.
What is needed is an improved lubricating film between the transducer carrier and the disk which minimizes wear of the protective overcoat and the underlying magnetic film on the disk, and which generates a low stiction interface when used with CSS disk files.
The above description summarizes the general operation of and problems associated with disk files. With this as background, a second unrelated technology area important to an understanding of the present invention is the relatively recent field of study relating to fullerenes. Fullerenes are a class of pure carbon molecules wherein the carbon atoms form a closed shell. The most stable and abundantly produced fullerenes are the C.sub.60 molecule, which has the shape of a soccer ball and is also referred to as a "buckyball," and the C.sub.70 molecule, which has the general shape of a rugby ball. The history of the discovery of fullerenes and a summary of their properties and potential applications are described in "Fullerenes", Scientific American, October, 1991, pp. 54-63 and "BUCKYBALL-The Magic Molecule," Popular Science, August, 1991, p.52ff.